This is my reply to SIRguru (forgot to copy to TechNet):
thanks...
with the environment of OEM, contract, subcontract, distributor multi-layer
supplyer structure, it is very painful (keep on changing manufacture
location and sub-package house, lead finishing house, moulding compounds,
flux, particularly, at down south, far east...you know what I am talking
about...).
jk
All,
with warehouse type of distributor, multi-vendor, multi-location manufacture
of the same parts (called "equivalent" parts), it is not realistic to
specify use specific type of flux compatible with in house assembly cleaning
process...(identify what type of flux residue on what Fab is pain) As for
specify the ug/sq inch ionics, we need standard, really...
jk
At 09:08 AM 2/23/00 +0100, you wrote:
>Bernhard
>
>I could not disagree with you more. Many components I have tested with
>an ionic contamination tester have revealed levels of 12 - 24 ug/cm2 eq.
>NaCl (compared with c. 1,5 ug/cm2 eq. NaCl as typical old spec levels).
>Many component manufacturers use hydrochloride-activated W/S fluxes for
>hot tinning with just a perfunctory single spray of water, rarely
>changing the water. These residues may be totally insoluble in solvents
>and, in time, even in water. They may, however, alter the reactivity of
>the subsequent soldering flux and, in the case of "no-clean", give a
>very reactive residue, leading to untold problems. I pointed this
>problem out in three of my books published in the 1980s and this is the
>reason my company, at that time, developed a tester for components.
>
>IMHO, there is no such thing as "normal" contamination. The only things
>that should remain on a "no-clean" assembly are the flux residues and
>by-products. "No-clean" is a misnomer, especially if you wish
>reliability: it means that you displace the cleaning processes to the
>bare boards and other components before assembly and you make sure your
>assembly process does not introduce any other contamination. Only that
>way can you be sure that the flux residues are benign enough to perform
>as the manufacturer intended.
>
>This is the main reason why SIR testing is, in many cases, useless to
>qualify a flux: you qualify it under lab conditions, totally ignoring
>the fact that its behavious will alter in practice due to it mixing with
>external contaminants not present on your test vehicles.
>
>I cannot emphasise these points too strongly: I have seen much damage
>caused by contaminated components, even to the point that the component
>leads themselves have been corroded through. And don't think that this
>is confined to hot-tinned ones - I have seen electroplated leads equally
>bad.
>
>Now, there's something for Doug, Graham and others to chew the rag over!
>
>Brian
>
>> Wanner Bernhard wrote:
>>
>> Probably its not a real problem, because...
>>
>> * if you are cleaning your pwa's anyway, you will clean also the
>> components,
>> * if you use clean-free, you will take accept also all your
>> "normal" internal contaminants (flux, fingerprints ..) and most
>> component-contaminants will be at a similar level/kind.
>>
>> I like it, Dougs :"...YOU determine ..". hehe, that's exactely what
>> you have to do, but instead of to write own standards I would refer to
>> the golden IPC-octuple (you don't know it? so what!: IPC-2221, -2222,
>> -6011, -6012, -4101, -A-600, -A-610, J-STD-001, all class 2, and
>> IPC-D-279 + IPC-HBK-001 as guidelines).
>>
>> Bernhard
>>
>> -----Ursprüngliche Nachricht-----
>> Von: Douglas Pauls [SMTP:[log in to unmask]]
>> Gesendet am: Dienstag, 22. Februar 2000 19:42
>> An: [log in to unmask]
>> Betreff: Re: [TN] components cleanliness
>>
>> In a message dated 02/22/2000 11:50:09 AM US Eastern Standard
>> Time,
>> [log in to unmask] writes:
>>
>> > Is IPC has requirement for component cleanliness? I have
>> checked archives
>> > of TechNet. No IPC requirement in Sept. 1998. Anything
>> changed? As Bev
>> > Christian stated 2 years ago:
>> > "No company can really afford to carry a complete set of its
>> own standards
>> > any more and with the contract manufacturing industry out
>> there, it doesn't
>> > even make sense to try and do it."
>> > Help! (with components comming from anywhere and everywhere,
>> standards
>> are
>> > needed)
>>
>> Joyce,
>> Don't hold your breath. With the move towards performance based
>> specifications, most IPC assembly level specifications are going
>> the route of
>> having the assembler or OEM define for their hardware what
>> cleanliness
>> measures are to be used and what cleanliness requirements are for
>> their
>> products. From a cleanliness standpoint, I don't foresee any
>> more "one size
>> fits all" cleanliness specs. Them days is gone. I think about
>> the best you
>> will see will be recommended protocols from the IPC on how YOU
>> determine
>> cleanliness of components and how YOU determine how clean your
>> components
>> need to be for your hardware.
>>
>> Doug Pauls
>> Technical Director
>> Contamination Studies Labs
>>
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>--
>Brian Ellis
>Protonique SA
>PO Box 78
>CH-1032 Romanel-sur-Lausanne, Switzerland
>Voice: +41 21-648 23 34 Fax: +41 21-648 24 11
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